The Duchess of Cornwall has cancelled a second official engagement this week on doctor's orders (PA/AAP)The Duchess is suffering from a chest infection which has become "progressively worse" (PA/AAP)

The Duchess is suffering from a chest infection which has become "progressively worse", Clarence House said in a statement.

It read: "The Duchess of Cornwall has been told by her doctor to cancel her engagements owing to a chest infection which has got progressively worse over the last few days. She will therefore not be at today's event with Harry and Meghan."

However, due to her worsening chest infection, the Duchess was forced to cancel another royal engagement later in the day and pulled out of a special 200th anniversary dinner of the birth of Prince Albert.

Prince Harry and Meghan Markle attended the opening of the 91st Field of Remembrance at Westminster Abbey on Thursday (PA/AAP)It was the Duchess of Sussex's first time at the event and Prince Harry's seventh (PA/AAP)

Despite the Duchess of Cornwall having to skip the event Prince Harry led proceedings for his seventh time at the Field of Remembrance service at Westminster Abbey, dressed in his military uniform.